Examples of typical known systems for transmitting power between two devices by bringing the devices close to each other include magnetic-field-coupling power transmission systems in which, using an electromagnetic field, power is transmitted from the primary coil of a power transmitting device to the secondary coil of a power receiving device through a magnetic field. However, when power is transmitted through magnetic field coupling, since the magnitude of magnetic flux passing through the coils strongly influences electromotive force, high accuracy is required in the relative positional relationship between the primary coil and the secondary coil. In addition, since coils are used, it is difficult to reduce the sizes of the devices.
On the other hand, as disclosed in Patent Documents 1-3, electric-field-coupling wireless power transmission systems are known, in which power is transmitted from the coupling electrode of a power transmission unit to the coupling electrode of a load unit using a quasi-static electric field. In these systems, power is transmitted from the coupling electrode of a power transmitting device to the coupling electrode of a power receiving device through an electric field. This method allows the accuracy of the relative positional relationship between the coupling electrodes to be relatively low and allows the sizes and thicknesses of the coupling electrodes to be reduced.
FIG. 1 is a diagram illustrating the basic configuration of a power transmission system disclosed in Patent Document 1. This power transmission system is formed of a power transmitting device and a power receiving device. The power transmitting device includes a high-frequency high-voltage generating circuit 1, a passive electrode 2, and an active electrode 3. The power receiving device includes a high-frequency high-voltage load circuit 5, a passive electrode 7, and an active electrode 6. As a result of the active electrode 3 and the active electrode 6 being arranged close to each other with a high-voltage electric field region 4 therebetween, these two electrodes are coupled to each other through an electric field.